The BMW M70 V12 Engine: A History


BMW M70 V12 Engine: A Historical past of Innovation and Efficiency

In days passed by, some engineers in a big shed in Coventry, often known as Jaguar Automobiles, constructed what was thought of one of the best manufacturing engine on this planet – their 5.3 liter V12. Mercedes tried to surpass it however failed. In the meantime, BMW explored totally different choices, equivalent to combining two M20 sixes on a typical crankshaft, however they realized they wanted to assume additional forward.

How BMW Beat Mercedes-Benz to the Punch with its First V12 Engine

In the course of the early eighties, whereas growing the M70, BMW acknowledged that the SOHC M20 was turning into outdated and within the technique of being changed by a 24-valve M50 successor. Not solely that, however they have been additionally engaged on an all-new M40 four-cylinder OHC unit to interchange the M10 that had been in manufacturing since 1962, which incorporates fashions just like the 2002 and Neue Klasse.

The M40 engine boasted a number of benefits: it was smaller, lighter, quieter, extra highly effective, and extra fuel-efficient, because of its intelligent piston crown and combustion chamber design. Moreover, it utilized finger rockers and hydraulic tappets. Most significantly, it was designed for mass manufacturing. Then again, the V12 engine was at all times meant to be extra of a conceit undertaking than a best-seller. Consequently, the M70 V12 was based mostly on the M40 design and manufactured utilizing the identical tooling. Sure, self-importance performed a job. BMW aimed to outpace Mercedes-Benz and assemble the primary German V12 luxurious automobile, and so they achieved this feat 4 years forward of their competitors.

The M70 V12 Engine: A Easy, Dependable Powerhouse

Nonetheless, because the E32 750iL was being launched in late 1987, BMW was already growing a brand new technology of all-alloy V8 32-valve engines to interchange the previous M30 sixes. Thus, the M70 was designed as a comparatively low-cost undertaking that closely relied on high-volume manufacturing elements, a lot of which have been derived from the M40 itself. These included connecting rods, rocker arms, and valves. Though the pistons shared an analogous design, they have been comprised of a unique alloy and featured barely offset gudgeon pins, leading to asymmetrical pistons.

The M70 utilized an alloy block forged in Alusil silicon alloy, which concerned boring, honing, and ending the cylinders with out metal sleeves. In the course of the ending honing course of, tiny silicon crystals have been revealed, offering a floor on which the particular pistons and rings may run. The lengthy metal crankshaft was counterweighted, and every financial institution’s overhead camshaft was pushed by a simplex curler chain linked to the crankshaft, with a second chain driving the oil pump.

Rocker fingers and hydraulic tappets operated the valves, whereas the cams have been lubricated by an oil spray bar secured to the cam finding caps and equipped with pressurized oil. The oil filter housing was remotely mounted, geared up with versatile provide and return pipes. Cooling was facilitated by a mixed water pump and thermostat unit with an 85-degree thermostat. The M70’s bore and stroke of 84 mm/75 mm resulted in a cubic capability of 4988 cc, and it had a comparatively low compression ratio of 8.8:1.

The M70 V12 Engine: A Legend within the Making

On the time, {the electrical} and engine administration system of the M70 V12 was state-of-the-art. It launched the usage of EML fly-by-wire throttle, eliminating the necessity for cables between the engine and the accelerator pedal. Bosch Motronic 1.7 was employed, with two programs utilized, one for every financial institution. This strategy concerned two units of plug leads, distributor caps, and crankshaft sensors. The intention behind this design was to make sure that even when one financial institution malfunctioned, the engine would nonetheless ship a full 150 bhp, holding the car operational.

When it was launched in 1987, the M70 V12 produced 300 bhp at 5200 rpm, with 450 nm of torque at 4100 rpm. Compared, the Mercedes 560SEL, with its 5547 cc V8, generated 275 bhp and 430 nm of torque. BMW was actually on the best path, however did they surpass Jaguar? The M70 was clean like a six-cylinder engine, whereas the Jaguar unit had a extra mercurial nature and was notably quieter. It was an enchancment, however deciding which was preferable proved to be a difficult query.

Because the 750i continued to promote steadily, there was a necessity for a extra highly effective unit for the 850i. In 1993, the 850CSi was launched, housing the 380 bhp S70 engine, which was developed in collaboration with BMW Motorsport. The S70 B56 was a hand-built 5.6 liter M70 engine with a displacement of 5576 cc achieved via an elevated bore and stroke of 86mm and 80mm, respectively. The compression ratio was raised to 9.8:1, and the Bosch Motronic 1.7 administration system was optimized to supply 380 bhp at 5300 rpm, together with 550 nm of torque at 4000 rpm. The cylinder heads obtained re-profiled camshafts, whereas the valves remained unchanged. Nonetheless, manufacturing of the 850CSi was restricted to only over 1500 automobiles because of non-compliance with US emissions laws.

The M73 V12 Engine: A Extra Highly effective and Environment friendly Evolution

In 1994, the unique 750i was succeeded by the all-new E38 model, that includes the brand new 5.4 liter M73 engine. Previous to the E38 launch, this spinoff was first put in within the 850i in January 1994 to make sure its readiness. Not like the 5.6-liter engine, the bore and stroke have been totally different, measuring 85mm and 79mm, respectively, leading to a displacement of 5379 cc. The compression ratio was elevated to 10:1 for improved effectivity. The ability output was rated at 326 bhp at 5000 rpm, with torque growing to a powerful 490 nm.

The M73 engine integrated oil cooling jets for the pistons and featured an enhanced Bosch Motronic M5.2 system with knock sensors within the cylinder heads. Measures have been taken to scale back friction, equivalent to using smaller diameter camshaft bearings and curler rockers from the brand new M43 four-cylinder unit. Moreover, softer double valve springs and lighter exhaust valves have been employed, together with secondary air injection for emissions management. Metal tubular exhaust manifolds have been chosen for his or her skill to warmth up extra shortly in comparison with forged iron sorts, additional enhancing efficiency.

Why the BMW V12 Engine Is Nonetheless So Fashionable In the present day

It was a great engine, the M70 and its offshoots. Easy, dependable and with spectacular high finish shove, it was additionally somewhat too keen on petrol and the Lexus LS400 of 1989 prompted panic in Germany – the BMW V8’s would just about outpoint the previous V12 on most counts. BMW would revive the V12 in later years with the E65 760i and it’s magic N73 and, while you’d deserve an Iron Cross for proudly owning and feeding one now, think about that the primary proprietor paid inn the neighborhood of $100,000 simply so that you or I can purchase it now for peanuts. Attempt eBay, you realize you need one.


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